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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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package javax.xml.namespace;

import java.io.Serializable;
import java.security.AccessController;
import java.security.PrivilegedAction;

import javax.xml.XMLConstants;

/**
 * <p><code>QName</code> represents a <strong>qualified name</strong>
 * as defined in the XML specifications: <a
 * href="http://www.w3.org/TR/xmlschema-2/#QName">XML Schema Part2:
 * Datatypes specification</a>, <a
 * href="http://www.w3.org/TR/REC-xml-names/#ns-qualnames">Namespaces
 * in XML</a>, <a
 * href="http://www.w3.org/XML/xml-names-19990114-errata">Namespaces
 * in XML Errata</a>.</p>
 *
 * <p>The value of a <code>QName</code> contains a <strong>Namespace
 * URI</strong>, <strong>local part</strong> and
 * <strong>prefix</strong>.</p>
 *
 * <p>The prefix is included in <code>QName</code> to retain lexical
 * information <strong><em>when present</em></strong> in an {@link
 * javax.xml.transform.Source XML input source}. The prefix is
 * <strong><em>NOT</em></strong> used in {@link #equals(Object)
 * QName.equals(Object)} or to compute the {@link #hashCode()
 * QName.hashCode()}.  Equality and the hash code are defined using
 * <strong><em>only</em></strong> the Namespace URI and local part.</p>
 *
 * <p>If not specified, the Namespace URI is set to {@link
 * javax.xml.XMLConstants#NULL_NS_URI XMLConstants.NULL_NS_URI}.
 * If not specified, the prefix is set to {@link
 * javax.xml.XMLConstants#DEFAULT_NS_PREFIX
 * XMLConstants.DEFAULT_NS_PREFIX}.</p>
 *
 * <p><code>QName</code> is immutable.</p>
 *
 * @author <a href="mailto:Jeff.Suttor@Sun.com">Jeff Suttor</a>
 * @version $Revision: 1.8 $, $Date: 2010/03/18 03:06:17 $
 * @see <a href="http://www.w3.org/TR/xmlschema-2/#QName"> XML Schema Part2: Datatypes
 * specification</a>
 * @see <a href="http://www.w3.org/TR/REC-xml-names/#ns-qualnames"> Namespaces in XML</a>
 * @see <a href="http://www.w3.org/XML/xml-names-19990114-errata"> Namespaces in XML Errata</a>
 * @since 1.5
 */

public class QName implements Serializable {

  /**
   * <p>Stream Unique Identifier.</p>
   *
   * <p>Due to a historical defect, QName was released with multiple
   * serialVersionUID values even though its serialization was the
   * same.</p>
   *
   * <p>To workaround this issue, serialVersionUID is set with either
   * a default value or a compatibility value.  To use the
   * compatiblity value, set the system property:</p>
   *
   * <code>com.sun.xml.namespace.QName.useCompatibleSerialVersionUID=1.0</code>
   *
   * <p>This workaround was inspired by classes in the javax.management
   * package, e.g. ObjectName, etc.
   * See CR6267224 for original defect report.</p>
   */
  private static final long serialVersionUID;
  /**
   * <p>Default <code>serialVersionUID</code> value.</p>
   */
  private static final long defaultSerialVersionUID = -9120448754896609940L;
  /**
   * <p>Compatibility <code>serialVersionUID</code> value.</p>
   */
  private static final long compatibleSerialVersionUID = 4418622981026545151L;
  /**
   * <p>Flag to use default or campatible serialVersionUID.</p>
   */
  private static boolean useDefaultSerialVersionUID = true;

  static {
    try {
      // use a privileged block as reading a system property
      String valueUseCompatibleSerialVersionUID = (String) AccessController.doPrivileged(
          new PrivilegedAction() {
            public Object run() {
              return System
                  .getProperty("com.sun.xml.namespace.QName.useCompatibleSerialVersionUID");
            }
          }
      );
      useDefaultSerialVersionUID =
          (valueUseCompatibleSerialVersionUID != null && valueUseCompatibleSerialVersionUID
              .equals("1.0")) ? false : true;
    } catch (Exception exception) {
      // use default if any Exceptions
      useDefaultSerialVersionUID = true;
    }

    // set serialVersionUID to desired value
    if (useDefaultSerialVersionUID) {
      serialVersionUID = defaultSerialVersionUID;
    } else {
      serialVersionUID = compatibleSerialVersionUID;
    }
  }

  /**
   * <p>Namespace URI of this <code>QName</code>.</p>
   */
  private final String namespaceURI;

  /**
   * <p>local part of this <code>QName</code>.</p>
   */
  private final String localPart;

  /**
   * <p>prefix of this <code>QName</code>.</p>
   */
  private final String prefix;

  /**
   * <p><code>QName</code> constructor specifying the Namespace URI
   * and local part.</p>
   *
   * <p>If the Namespace URI is <code>null</code>, it is set to
   * {@link javax.xml.XMLConstants#NULL_NS_URI
   * XMLConstants.NULL_NS_URI}.  This value represents no
   * explicitly defined Namespace as defined by the <a
   * href="http://www.w3.org/TR/REC-xml-names/#ns-qualnames">Namespaces
   * in XML</a> specification.  This action preserves compatible
   * behavior with QName 1.0.  Explicitly providing the {@link
   * javax.xml.XMLConstants#NULL_NS_URI
   * XMLConstants.NULL_NS_URI} value is the preferred coding
   * style.</p>
   *
   * <p>If the local part is <code>null</code> an
   * <code>IllegalArgumentException</code> is thrown.
   * A local part of "" is allowed to preserve
   * compatible behavior with QName 1.0. </p>
   *
   * <p>When using this constructor, the prefix is set to {@link
   * javax.xml.XMLConstants#DEFAULT_NS_PREFIX
   * XMLConstants.DEFAULT_NS_PREFIX}.</p>
   *
   * <p>The Namespace URI is not validated as a
   * <a href="http://www.ietf.org/rfc/rfc2396.txt">URI reference</a>.
   * The local part is not validated as a
   * <a href="http://www.w3.org/TR/REC-xml-names/#NT-NCName">NCName</a>
   * as specified in <a href="http://www.w3.org/TR/REC-xml-names/">Namespaces
   * in XML</a>.</p>
   *
   * @param namespaceURI Namespace URI of the <code>QName</code>
   * @param localPart local part of the <code>QName</code>
   * @throws IllegalArgumentException When <code>localPart</code> is <code>null</code>
   * @see #QName(String namespaceURI, String localPart, String prefix) QName(String namespaceURI,
   * String localPart, String prefix)
   */
  public QName(final String namespaceURI, final String localPart) {
    this(namespaceURI, localPart, XMLConstants.DEFAULT_NS_PREFIX);
  }

  /**
   * <p><code>QName</code> constructor specifying the Namespace URI,
   * local part and prefix.</p>
   *
   * <p>If the Namespace URI is <code>null</code>, it is set to
   * {@link javax.xml.XMLConstants#NULL_NS_URI
   * XMLConstants.NULL_NS_URI}.  This value represents no
   * explicitly defined Namespace as defined by the <a
   * href="http://www.w3.org/TR/REC-xml-names/#ns-qualnames">Namespaces
   * in XML</a> specification.  This action preserves compatible
   * behavior with QName 1.0.  Explicitly providing the {@link
   * javax.xml.XMLConstants#NULL_NS_URI
   * XMLConstants.NULL_NS_URI} value is the preferred coding
   * style.</p>
   *
   * <p>If the local part is <code>null</code> an
   * <code>IllegalArgumentException</code> is thrown.
   * A local part of "" is allowed to preserve
   * compatible behavior with QName 1.0. </p>
   *
   * <p>If the prefix is <code>null</code>, an
   * <code>IllegalArgumentException</code> is thrown.  Use {@link
   * javax.xml.XMLConstants#DEFAULT_NS_PREFIX
   * XMLConstants.DEFAULT_NS_PREFIX} to explicitly indicate that no
   * prefix is present or the prefix is not relevant.</p>
   *
   * <p>The Namespace URI is not validated as a
   * <a href="http://www.ietf.org/rfc/rfc2396.txt">URI reference</a>.
   * The local part and prefix are not validated as a
   * <a href="http://www.w3.org/TR/REC-xml-names/#NT-NCName">NCName</a>
   * as specified in <a href="http://www.w3.org/TR/REC-xml-names/">Namespaces
   * in XML</a>.</p>
   *
   * @param namespaceURI Namespace URI of the <code>QName</code>
   * @param localPart local part of the <code>QName</code>
   * @param prefix prefix of the <code>QName</code>
   * @throws IllegalArgumentException When <code>localPart</code> or <code>prefix</code> is
   * <code>null</code>
   */
  public QName(String namespaceURI, String localPart, String prefix) {

    // map null Namespace URI to default
    // to preserve compatibility with QName 1.0
    if (namespaceURI == null) {
      this.namespaceURI = XMLConstants.NULL_NS_URI;
    } else {
      this.namespaceURI = namespaceURI;
    }

    // local part is required.
    // "" is allowed to preserve compatibility with QName 1.0
    if (localPart == null) {
      throw new IllegalArgumentException(
          "local part cannot be \"null\" when creating a QName");
    }
    this.localPart = localPart;

    // prefix is required
    if (prefix == null) {
      throw new IllegalArgumentException(
          "prefix cannot be \"null\" when creating a QName");
    }
    this.prefix = prefix;
  }

  /**
   * <p><code>QName</code> constructor specifying the local part.</p>
   *
   * <p>If the local part is <code>null</code> an
   * <code>IllegalArgumentException</code> is thrown.
   * A local part of "" is allowed to preserve
   * compatible behavior with QName 1.0. </p>
   *
   * <p>When using this constructor, the Namespace URI is set to
   * {@link javax.xml.XMLConstants#NULL_NS_URI
   * XMLConstants.NULL_NS_URI} and the prefix is set to {@link
   * javax.xml.XMLConstants#DEFAULT_NS_PREFIX
   * XMLConstants.DEFAULT_NS_PREFIX}.</p>
   *
   * <p><em>In an XML context, all Element and Attribute names exist
   * in the context of a Namespace.  Making this explicit during the
   * construction of a <code>QName</code> helps prevent hard to
   * diagnosis XML validity errors.  The constructors {@link
   * #QName(String namespaceURI, String localPart) QName(String
   * namespaceURI, String localPart)} and
   * {@link #QName(String namespaceURI, String localPart, String prefix)}
   * are preferred.</em></p>
   *
   * <p>The local part is not validated as a
   * <a href="http://www.w3.org/TR/REC-xml-names/#NT-NCName">NCName</a>
   * as specified in <a href="http://www.w3.org/TR/REC-xml-names/">Namespaces
   * in XML</a>.</p>
   *
   * @param localPart local part of the <code>QName</code>
   * @throws IllegalArgumentException When <code>localPart</code> is <code>null</code>
   * @see #QName(String namespaceURI, String localPart) QName(String namespaceURI, String localPart)
   * @see #QName(String namespaceURI, String localPart, String prefix) QName(String namespaceURI,
   * String localPart, String prefix)
   */
  public QName(String localPart) {
    this(
        XMLConstants.NULL_NS_URI,
        localPart,
        XMLConstants.DEFAULT_NS_PREFIX);
  }

  /**
   * <p>Get the Namespace URI of this <code>QName</code>.</p>
   *
   * @return Namespace URI of this <code>QName</code>
   */
  public String getNamespaceURI() {
    return namespaceURI;
  }

  /**
   * <p>Get the local part of this <code>QName</code>.</p>
   *
   * @return local part of this <code>QName</code>
   */
  public String getLocalPart() {
    return localPart;
  }

  /**
   * <p>Get the prefix of this <code>QName</code>.</p>
   *
   * <p>The prefix assigned to a <code>QName</code> might
   * <strong><em>NOT</em></strong> be valid in a different
   * context. For example, a <code>QName</code> may be assigned a
   * prefix in the context of parsing a document but that prefix may
   * be invalid in the context of a different document.</p>
   *
   * @return prefix of this <code>QName</code>
   */
  public String getPrefix() {
    return prefix;
  }

  /**
   * <p>Test this <code>QName</code> for equality with another
   * <code>Object</code>.</p>
   *
   * <p>If the <code>Object</code> to be tested is not a
   * <code>QName</code> or is <code>null</code>, then this method
   * returns <code>false</code>.</p>
   *
   * <p>Two <code>QName</code>s are considered equal if and only if
   * both the Namespace URI and local part are equal. This method
   * uses <code>String.equals()</code> to check equality of the
   * Namespace URI and local part. The prefix is
   * <strong><em>NOT</em></strong> used to determine equality.</p>
   *
   * <p>This method satisfies the general contract of {@link
   * java.lang.Object#equals(Object) Object.equals(Object)}</p>
   *
   * @param objectToTest the <code>Object</code> to test for equality with this <code>QName</code>
   * @return <code>true</code> if the given <code>Object</code> is equal to this <code>QName</code>
   * else <code>false</code>
   */
  public final boolean equals(Object objectToTest) {
    if (objectToTest == this) {
      return true;
    }

    if (objectToTest == null || !(objectToTest instanceof QName)) {
      return false;
    }

    QName qName = (QName) objectToTest;

    return localPart.equals(qName.localPart)
        && namespaceURI.equals(qName.namespaceURI);
  }

  /**
   * <p>Generate the hash code for this <code>QName</code>.</p>
   *
   * <p>The hash code is calculated using both the Namespace URI and
   * the local part of the <code>QName</code>.  The prefix is
   * <strong><em>NOT</em></strong> used to calculate the hash
   * code.</p>
   *
   * <p>This method satisfies the general contract of {@link
   * java.lang.Object#hashCode() Object.hashCode()}.</p>
   *
   * @return hash code for this <code>QName</code> <code>Object</code>
   */
  public final int hashCode() {
    return namespaceURI.hashCode() ^ localPart.hashCode();
  }

  /**
   * <p><code>String</code> representation of this
   * <code>QName</code>.</p>
   *
   * <p>The commonly accepted way of representing a <code>QName</code>
   * as a <code>String</code> was
   * <a href="http://jclark.com/xml/xmlns.htm">defined</a>
   * by James Clark.  Although this is not a <em>standard</em>
   * specification, it is in common use, e.g. {@link
   * javax.xml.transform.Transformer#setParameter(String name, Object value)}.
   * This implementation represents a <code>QName</code> as:
   * "{" + Namespace URI + "}" + local part.  If the Namespace URI
   * <code>.equals(XMLConstants.NULL_NS_URI)</code>, only the
   * local part is returned.  An appropriate use of this method is
   * for debugging or logging for human consumption.</p>
   *
   * <p>Note the prefix value is <strong><em>NOT</em></strong>
   * returned as part of the <code>String</code> representation.</p>
   *
   * <p>This method satisfies the general contract of {@link
   * java.lang.Object#toString() Object.toString()}.</p>
   *
   * @return <code>String</code> representation of this <code>QName</code>
   */
  public String toString() {
    if (namespaceURI.equals(XMLConstants.NULL_NS_URI)) {
      return localPart;
    } else {
      return "{" + namespaceURI + "}" + localPart;
    }
  }

  /**
   * <p><code>QName</code> derived from parsing the formatted
   * <code>String</code>.</p>
   *
   * <p>If the <code>String</code> is <code>null</code> or does not conform to
   * {@link #toString() QName.toString()} formatting, an
   * <code>IllegalArgumentException</code> is thrown.</p>
   *
   * <p><em>The <code>String</code> <strong>MUST</strong> be in the
   * form returned by {@link #toString() QName.toString()}.</em></p>
   *
   * <p>The commonly accepted way of representing a <code>QName</code>
   * as a <code>String</code> was
   * <a href="http://jclark.com/xml/xmlns.htm">defined</a>
   * by James Clark.  Although this is not a <em>standard</em>
   * specification, it is in common use, e.g. {@link
   * javax.xml.transform.Transformer#setParameter(String name, Object value)}.
   * This implementation parses a <code>String</code> formatted
   * as: "{" + Namespace URI + "}" + local part.  If the Namespace
   * URI <code>.equals(XMLConstants.NULL_NS_URI)</code>, only the
   * local part should be provided.</p>
   *
   * <p>The prefix value <strong><em>CANNOT</em></strong> be
   * represented in the <code>String</code> and will be set to
   * {@link javax.xml.XMLConstants#DEFAULT_NS_PREFIX
   * XMLConstants.DEFAULT_NS_PREFIX}.</p>
   *
   * <p>This method does not do full validation of the resulting
   * <code>QName</code>.
   * <p>The Namespace URI is not validated as a
   * <a href="http://www.ietf.org/rfc/rfc2396.txt">URI reference</a>.
   * The local part is not validated as a
   * <a href="http://www.w3.org/TR/REC-xml-names/#NT-NCName">NCName</a>
   * as specified in
   * <a href="http://www.w3.org/TR/REC-xml-names/">Namespaces in XML</a>.</p>
   *
   * @param qNameAsString <code>String</code> representation of the <code>QName</code>
   * @return <code>QName</code> corresponding to the given <code>String</code>
   * @throws IllegalArgumentException When <code>qNameAsString</code> is <code>null</code> or
   * malformed
   * @see #toString() QName.toString()
   */
  public static QName valueOf(String qNameAsString) {

    // null is not valid
    if (qNameAsString == null) {
      throw new IllegalArgumentException(
          "cannot create QName from \"null\" or \"\" String");
    }

    // "" local part is valid to preserve compatible behavior with QName 1.0
    if (qNameAsString.length() == 0) {
      return new QName(
          XMLConstants.NULL_NS_URI,
          qNameAsString,
          XMLConstants.DEFAULT_NS_PREFIX);
    }

    // local part only?
    if (qNameAsString.charAt(0) != '{') {
      return new QName(
          XMLConstants.NULL_NS_URI,
          qNameAsString,
          XMLConstants.DEFAULT_NS_PREFIX);
    }

    // Namespace URI improperly specified?
    if (qNameAsString.startsWith("{" + XMLConstants.NULL_NS_URI + "}")) {
      throw new IllegalArgumentException(
          "Namespace URI .equals(XMLConstants.NULL_NS_URI), "
              + ".equals(\"" + XMLConstants.NULL_NS_URI + "\"), "
              + "only the local part, "
              + "\""
              + qNameAsString.substring(2 + XMLConstants.NULL_NS_URI.length())
              + "\", "
              + "should be provided.");
    }

    // Namespace URI and local part specified
    int endOfNamespaceURI = qNameAsString.indexOf('}');
    if (endOfNamespaceURI == -1) {
      throw new IllegalArgumentException(
          "cannot create QName from \""
              + qNameAsString
              + "\", missing closing \"}\"");
    }
    return new QName(
        qNameAsString.substring(1, endOfNamespaceURI),
        qNameAsString.substring(endOfNamespaceURI + 1),
        XMLConstants.DEFAULT_NS_PREFIX);
  }
}
